I can't remember how much time I spent thinking about it, but if I were to reenact my state of mind at the time, I probably concluded something like, "Without transactions, I'll have to write more code to make sure the ID in both tables stays in sync, and I'll have to send 2 separate INSERTs (sequentially) for every record added, and if the first one fails, I need to handle that, and if the 2nd one fails, I need to handle that differently, and... fuck it. I'll just promise to be good and not use FKs"

Or something. I can't remember the details, but I was (and still am) very averse to complexity in my application code.